Abrasive cutter and method for cutting through a rail of a track

ABSTRACT

An abrasive cutter for cutting a rail of a track includes a drive for driving a cutting disc holder in rotation. A cutting disc is attached to the cutting disc holder with at least one clamping element. The drive is directly coupled to the cutting disc holder and has a maximum transverse extent which is at most equal to a diameter of at least one clamping element. The drive has an electric drive motor with a power density P Spez ≥0.5 kW/kg. The abrasive cutter allows a reliable, efficient, user-friendly and low-maintenance through-cutting of a rail of a track.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation, under 35 U.S.C. § 120, of copending International Patent Application PCT/EP2020/062542, filed May 6, 2020, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 20 2019 103 132.8, filed Jun. 4, 2019; the prior applications are herewith incorporated by reference in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The invention concerns an abrasive cutter and method for cutting through a rail of a track.

Abrasive cutters with direct drive for cutting through a rail of a track are known from the prior art. Such abrasive cutters have a hydraulic drive which is actively connected to the shaft of the cutting disc. The production and maintenance of known abrasive cutters are complex.

European published application EP 3 216 567 A1 discloses a disc cutter in which the cutting disc is driven in rotation by an electric drive motor. The electric drive motor is coupled directly to a cutting disc holder by means of a drive shaft. The rotational axis of the cutting disc or cutting disc holder runs either coaxially to the drive axis of the drive motor or is offset in parallel to the drive axis.

SUMMARY OF THE INVENTION

It is an object of the present invention to create a simple abrasive cutter which allows through-cutting of the rail of a track in a reliable, efficient, user-friendly and low-maintenance fashion.

This object may be achieved by an abrasive cutter for cutting through a rail of a track, with

a base body,

a cutting disc holder for mounting a cutting disc, and

a drive for driving the cutting disc holder in rotation about a rotational axis, wherein

the drive is directly coupled to the cutting disc holder,

the drive comprises an electric drive motor,

a drive axis of the electric drive motor and the rotational axis align, and

wherein the drive has a maximum transverse extent which is at most equal to a diameter of at least one clamping element for fixing the cutting disc to the cutting disc holder, and the electric drive motor has a power density P_(Spez), wherein P_(Spez)≥0.5 kW/kg.

The abrasive cutter according to the invention comprises an electric drive motor as the drive. The electric drive motor has a drive shaft and a drive axis, wherein the drive shaft is directly coupled to the cutting disc holder. Because the drive axis and the rotational axis of the cutting disc holder are aligned, a simple force transmission is achieved between the drive shaft and the cutting disc holder. Aligned or congruent means that the rotational axis is coaxial or identical to the drive axis. In particular, the electric drive motor is a brushless electric motor.

Because of the use of an electric drive motor, in comparison with a hydraulic drive, no additional elements, such as for example hydraulic lines, nozzles or valves, need be fitted in the abrasive cutter. The omission of these additional elements at the same time eliminates the problem of leakage and gap losses caused for example by a change in viscosity following temperature changes.

The reduction of additional elements has the further advantage that the abrasive cutter has lower energy losses and hence a higher efficiency. In particular, the efficiency of the abrasive cutter is over 90%, in particular over 95%, advantageously over 99%. Thus the abrasive cutter also has a lower energy consumption owing to the electric drive motor. At the same time, because of the omission of additional elements, the abrasive cutter comprises fewer components, in particular fewer wearing parts, whereby the maintenance complexity and maintenance cost may be significantly lowered and the time between individual service intervals can be extended. At the same time, the abrasive cutter has a lower overall weight.

In addition, the use of an electric drive motor eliminates the problem affecting known abrasive cutters, that these are often subject to pressure and movement fluctuations, whereby switching impacts and uneven movements occur. This avoids a tilting of the cutting disc and at the same time guarantees that the rail can be cut through in a reliable and efficient fashion.

The drive axis runs coaxially to the rotational axis. Because the maximum transverse extent of the drive is at most equal to the diameter of the at least one clamping element for fixing the cutting disc to the cutting disc holder, it is avoided that the drive or its housing protrudes into the cutting region of the cutting disc and reduces the cutting region. This therefore guarantees that the cutting disc, the diameter of which reduces successively due to wear during through-cutting of the rail, is utilized to the optimum. In other words, there is no restriction in cutting depth. The maximum transverse extent of the drive is in particular reduced by the high power density P_(Spez) of the electric drive motor.

Preferably, the abrasive cutter is configured for use of cutting discs with a maximum nominal diameter D_(N). For the maximum transverse extent E, in particular E≤0.6·D_(N), in particular E≤0.5·D_(N), and in particular E≤0.4·D_(N). Preferably, E≤0.2 D_(N). The maximum transverse extent is defined in particular perpendicularly to the drive axis or rotational axis and/or in the direction of the plane of symmetry of a cutting region of a cutting disc.

Preferably, the drive comprises the electric drive motor and a housing in which the electric drive motor is arranged and in particular mounted. The electric drive motor comprises a stator and a rotor. The drive shaft is connected to the rotor or is part of the rotor. Preferably, the stator delimits an interior in which the rotor is arranged. The rotor thus forms an internal rotor. The rotor preferably comprises permanent magnets. The permanent magnets are in particular attached to the drive shaft. The stator preferably comprises electromagnets.

The electric drive motor has a high power density or high specific power P_(Spez). The power density is the ratio of the nominal power P of the electric drive motor to its mass M. For the power density of the electric drive motor, P_(Spez)≥0.5 kW/kg, advantageously P_(Spez)≥0.8 kW/kg, and advantageously P_(Spez)≥1.0 kW/kg. Preferably, the electric drive motor has a nominal power P, wherein P≥2 kW, in particular P≤3 kW, and in particular P≥5 kW. For the nominal power P, preferably P≤10 kW, in particular P≤8 kW, in particular P≤6 kW, and in particular P≤4 kW. Because of the comparatively low weight, the abrasive cutter is user-friendly and easy to guide. The drive or electric drive motor, because of its compactness, guarantees that the cutting depth is not reduced.

Because of the direct coupling of the drive, the use of transmission elements can be largely omitted and their number reduced to a minimum. Consequently, the use of adjustable or endless transmission elements such as gear mechanisms or belts is no longer required, since the torque is transmitted directly from the drive to the cutting disc holder via the drive shaft.

Because of the direct coupling of the drive to the cutting disc holder, it is necessary for the drive to be arranged in the region of the rotational axis of the cutting disc or cutting disc holder. This has the advantage that the abrasive cutter has an optimal weight distribution, since the center of gravity of the abrasive cutter is shifted in the direction of the rotational axis. This allows through-cutting of the rail of the track in a reliable, efficient and at the same time user-friendly fashion.

The term “directly coupled” in particular means avoiding transmission elements as far as possible, or reducing these to a minimum. In addition, the term includes in particular an indirect or direct intermeshing, in particular an indirect or direct contact, of the cutting disc holder with the drive shaft.

The term “directly coupled” in particular excludes the use of endless transmission elements in the form of belts or chains, and the use of gear mechanisms, in particular adjustable gears which allow the setting of different translation ratios.

Advantageously, a translation ratio n is formed between the drive shaft and the cutting disc holder, wherein in particular n=1. A translation ratio of n=1 means that the electric drive motor is configured to have the rotational speed of the cutting disc. The translation ratio n is fixed, i.e. cannot be changed or adjusted.

The cutting disc is here actively connected to the cutting disc holder via at least one clamping element, whereby rotation of the cutting disc holder causes a rotation of the cutting disc. The at least one clamping element serves for fixing the cutting disc to the cutting disc holder. In particular, it is possible that the at least one clamping element is attached directly to the cutting disc holder, and the cutting disc is attached or clamped to the at least one clamping element. Thus the cutting disc is actively connected to the cutting disc holder indirectly via the at least one clamping element. The at least one clamping element may however also be configured such that the cutting disc can be attached directly thereby to the cutting disc holder. Advantageously, the at least one clamping element is attached to the cutting disc holder via a clamping element holder.

An advantageous embodiment comprises a first and a second clamping element, between which a cutting disc can be attached by clamping. The first and second clamping elements comprise for example, starting from the rotational axis in the direction of their respective outer edge, a deformation which runs towards the clamping disc and is sprung. This allows clamping discs of different thickness to be attached with vibration damping by means of the at least one clamping element.

It is possible that, in addition to the at least one clamping element, further elements are provided which are arranged between the cutting disc holder and the at least one clamping element, and/or between the at least one clamping element and the cutting disc.

The base body defines a base body plane G which runs through the base body and perpendicularly to the rotational axis. The base body plane G defines a first and a second side of the base body which lie opposite each other.

Advantageously, the abrasive cutter comprises a control unit for controlling the drive, wherein by means of the control unit, in particular two different rotational directions of the drive can be set.

The abrasive cutter serves for the manually-guided through-cutting of a rail.

An abrasive cutter configured such that a drive shaft of the electric drive motor is formed in one piece with the cutting disc holder, allows a reliable, efficient and low-maintenance through-cutting of the rail. Formed in one piece means that the cutting disc holder and the drive shaft are combined and inseparably connected together. The drive shaft and the cutting disc holder accordingly form a common shaft. Consequently, the drive torque is transmitted to the at least one clamping element and hence to the cutting disc solely via a shaft. This has the advantage that fewer components, in particular fewer wearing parts, are fitted in the abrasive cutter.

An abrasive cutter configured such that a drive shaft of the electric drive motor and the cutting disc holder are formed in two pieces, allows an efficient and low-maintenance through-cutting of the rail. A two-part design has the advantage that the cutting disc holder and the drive shaft can be replaced individually. Formed in two parts means that the drive shaft and the cutting disc holder are independent elements. The drive shaft and the cutting disc holder are actively connected together directly or indirectly at an engagement region. In particular, the drive shaft and the cutting disc holder may have a toothing in the engagement region, via which the drive shaft and the cutting disc holder make direct contact. The drive shaft and the cutting disc holder are connected together rotationally fixedly.

The drive shaft and the cutting disc holder are preferably actively connected together at the engagement region in a rotationally fixed or form-fit fashion via a connection which is secure against twisting. Advantageously, the direct active connection between the drive shaft and the cutting disc holder may be configured in form-fit fashion. In particular, at the engagement region, the drive shaft may be formed as a hollow shaft with internal toothing, while the cutting disc holder has external toothing which directly engages in the internal toothing of the drive shaft formed as a hollow shaft. It is also possible that the cutting disc holder is formed as a hollow shaft in the engagement region and has an internal toothing, wherein the drive shaft has an external toothing which engages in the internal toothing of the cutting disc holder formed as a hollow shaft. Alternatively, the active connection between the drive shaft and the cutting disc holder may be formed via a connecting component, for example a feather key.

An abrasive cutter configured such that the drive is arranged on the base body, in particular on a first side of the base body, allows a particularly reliable and efficient through-cutting of the rail. Advantageously, the drive comprises a housing by means of which the drive can be fixed via fixing means to a fixing region of the base body. Advantageously, damping elements are arranged between the housing and the fixing region, which reduces the transmission of vibrations from the drive to the base body. The fixing region is in particular arranged on a first side of the base body which is opposite the second side of the base body on which the cutting disc is arranged or can be fixed. The fixing region in particular has a width b which is smaller than the maximum width B of the base body. Thus the drive is arranged closer to the base body, which counters a shift in the center of gravity of the abrasive cutter in the direction of the first side. In particular, for the width b of the fixing region, b≤0.3·B, in particular b≤0.2·B, advantageously b≤0.1·B and/or b≤0.05·B. Preferably, a base body plane G runs perpendicularly to the rotational axis through the base body. The base body plane G in particular runs through the fixing region. The base body plane G defines the first side and the second side of the base body. The drive is preferably arranged on the first side, whereas a cutting disc can be attached to the cutting disc holder on the second side.

An abrasive cutter configured such that a first bearing is supported on a housing of the drive and a second bearing is supported on the base body, allows an efficient and user-friendly through-cutting of the rail. Because the second bearing is arranged outside the housing and in the base body, in particular on the fixing region, the drive is arranged closer to the base body plane, which counters a shift in the center of gravity of the abrasive cutter in the direction of the first side.

An abrasive cutter configured such that a first bearing and a second bearing are supported on a housing of the drive, allows a particularly efficient and low-maintenance through-cutting of the rail. Because the first and second bearings are arranged inside the housing of the drive, it is guaranteed that the drive can be replaced quickly and easily. In addition, the forces occurring during cutting of the rail are transmitted to the base body via the housing of the drive.

An abrasive cutter configured such that the electric drive motor is configured as a brushless electric motor, allows a particularly reliable and efficient through-cutting of the rail. The brushless electric motor requires little maintenance. Because of the brushless electric motor, it is guaranteed that the drive has a small transverse extent E and hence a substantially higher power density or specific power P_(Spez). In particular, for the power density P_(Spez) of the brushless electric motor, P_(Spez)≥0.5 kW/kg, in particular P_(Spez)≥0.8 kW/kg, and in particular P_(Spez)≥1.0 kW/kg. The brushless electric motor is in particular a BLDC motor.

An abrasive cutter configured such that for the power density P_(Spez) applies: P_(Spez)≥0.8 kW/kg, and in particular P_(Spez)≥1.0 kW/kg, allows a particularly reliable and efficient through-cutting of the rail. The higher the power density P_(Spez), the smaller and/or lighter the electric drive motor.

An abrasive cutter comprising at least one temperature sensor for determining a temperature of the drive and/or a temperature of a control unit, allows a particularly reliable and efficient through-cutting of the rail. The at least one temperature sensor serves to determine a temperature of the drive and/or the control unit during operation. The at least one determined temperature serves to avoid overheating of the abrasive cutter, in particular the drive or electric drive motor and/or the control unit, during through-cutting of a rail. Preferably, a temperature sensor is arranged on the drive, in particular inside a housing. The temperature sensor is in particular arranged on the electric drive motor. In addition or alternatively, a temperature sensor is preferably arranged on the control unit. The respective temperature sensor is in particular in signal connection with a warning element and/or the control unit. If a critical temperature of the drive and/or control unit is established by means of the respective temperature sensor, at least one countermeasure may be taken. Possible countermeasures are for example actuating the warning element to warn an operator, and/or reducing the consumable or emittable power of the electric drive motor, and/or shutting down the electric drive motor.

An abrasive cutter comprising a control unit for controlling the drive, in particular depending on a determined temperature, allows a particularly reliable and efficient through-cutting of a rail. Because the control unit actuates the drive or electric drive motor depending on a determined temperature, a simple temperature monitoring may be achieved. If the temperature sensor determines a temperature which exceeds a critical temperature or temperature limit value, by means of the control unit at least one countermeasure may be initiated. Possible countermeasures are for example actuating the warning element to warn an operator, reducing the consumable or emittable power of the electric drive motor, and/or shutting down the electric drive motor. The at least one countermeasure is active temporarily.

An abrasive cutter comprising a control unit which is configured such that an emittable power of the electric drive motor is reduced when a determined temperature exceeds a first temperature limit value, and/or such that the electric drive motor is shut down when a determined temperature exceeds a second temperature limit value, allows a particularly reliable and efficient through-cutting of a rail. If a determined temperature exceeds a first temperature limit value T_(G1), a further temperature rise can be countered by reducing the emittable or consumable power of the electric drive motor. The heat generated by the electric drive motor is reduced so that the electric drive motor and/or the control unit can cool down. The emittable power is preferably reduced provisionally or temporarily. This is achieved in particular depending on a predefined duration and/or depending on the temperature falling below a predefined temperature limit value. The limit value below which the temperature must fall here may be equal to or lower than the first temperature limit value T_(G1). Preferably, for the first temperature limit value T_(G1), 80° C.≤T_(G1)≤120° C., in particular 90° C.≤T_(G1)≤110°. For the maximum emittable or consumable reduced power P_(R), in particular 0.5·P≤P_(R)≤P, in particular 0.6·P≤P_(R)≤0.9·P, and in particular 0.7·P≤P_(R)≤0.8·P.

If a second temperature limit value T_(G2) is exceeded, the electric drive motor is shut down. This shut-down occurs in particular if a reduction in the emittable power of the abrasive cutter was unsuccessful. Preferably, the second temperature limit value T_(G2) is higher than the first temperature limit value T_(G1). Preferably, for the second temperature limit value T_(G2), 110° C.≤T_(G2)≤140° C., in particular 120° C.≤T_(G2)≤130° C. The electric drive motor is in particular shut down provisionally or temporarily. The temporary shut-down takes place for example depending on a predefined duration and/or depending on the temperature falling below a predefined temperature limit value. This limit value below which the temperature must fall may be equal to or lower than the second temperature limit value T_(G2). Preferably, the limit value below which the temperature must fall is lower than the first temperature limit value T_(G1).

When cutting through a rail, the control unit is preferably configured such that the electric drive motor is operated at least temporarily with a power P_(B) for which P≤P_(B)≤4·P, in particular 1.5·P≤P_(B)≤3.5·P, and in particular 2·P≤P_(B)≤3·P. P designates a nominal power of the electric drive motor.

An abrasive cutter comprising a cooling system for cooling the electric drive motor and/or a control unit, guarantees a reliable and efficient through-cutting of a rail. The cooling system is in particular configured as an active cooling system which produces a movement of a cooling fluid. Preferably, the cooling system comprises at least one cooling element which can be or is driven. The at least one cooling element serves in particular to produce the movement of the cooling fluid. Preferably, the at least one cooling element comprises a fan wheel. The fan wheel in particular generates an air stream for cooling the drive or electric drive motor and/or control unit. The at least one cooling element can be driven by means of the electric drive motor and/or by means of its own drive motor. Preferably, the at least one cooling element is attached to the drive axis of the electric drive motor and/or to the cutting disc holder. Preferably, the at least one cooling element is arranged on a side of the electric drive motor facing the cutting disc and/or on a side of the electric drive motor facing away from the cutting disc, concentrically to the drive axis or rotational axis. Preferably, the abrasive cutter comprises a fan, in particular an axial fan, with a fan wheel and an associated drive motor. The fan is for example arranged on the base body for cooling the control unit and/or for cooling the drive, and/or on the control unit and/or on the drive.

The invention is furthermore based on an object of creating a simple, reliable, user-friendly and efficient method for cutting through a rail of a track.

This object may be achieved by a method for cutting through a rail of a track, with the steps:

providing an abrasive cutter for cutting through a rail of a track, and

cutting through the rail by means of a cutting disc which is driven in rotation by means of the abrasive cutter.

The advantages of the method according to the invention correspond to the advantages of the abrasive cutter according to the invention as already described. The method according to the invention may in particular be refined by at least one feature which has been described in connection with the abrasive cutter according to the invention. When cutting through a rail, the electric drive motor is preferably operated at least temporarily with a power P_(B) for which P≤P_(B)≤4·P, in particular 1.5·P≤P_(B)≤3.5·P, and in particular 2·P≤P_(B)≤3·P, wherein P designates a nominal power of the electric drive motor.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in an abrasive cutter and a method for cutting through a rail of a track, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a perspective view of an abrasive cutter according to a first exemplary embodiment,

FIG. 2 shows a top view of the abrasive cutter from FIG. 1,

FIG. 3 shows a side view of the abrasive cutter from FIG. 1,

FIG. 4 shows a rear view of the abrasive cutter from FIG. 1,

FIG. 5 shows a section through the abrasive cutter along Line V-V in FIG. 2,

FIG. 6 shows a section through an abrasive cutter according to a second exemplary embodiment,

FIG. 7 shows a side view of an abrasive cutter according to a third exemplary embodiment,

FIG. 8 shows a section through the abrasive cutter along cut line VIII-VIII in FIG. 7, and

FIG. 9 shows a section through the abrasive cutter along cut line IX-IX in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 5 show an abrasive cutter 1 according to a first exemplary embodiment. The abrasive cutter 1 serves for cutting through a rail of a track. For reasons of clarity, the track is not depicted in the figures.

FIGS. 1 to 4 show the abrasive cutter comprising a base body 2, a drive 4 with the drive axis A₁, and a cutting disc 5. The drive 4 serves to drive the cutting disc 4 about a rotational axis A₂. According to the exemplary embodiment depicted, the rotational axis A₂ and the drive axis A₁ are aligned. The rotational axis A₂ is therefore identical to the drive axis A₁.

The base body 2 has a pivotable handle 8 for holding and manually guiding the abrasive cutter 1. The base body 2 defines a base body plane G which runs through the base body 2 and perpendicularly to the rotational axis A₂. The drive 4 and the cutting disc 5 are arranged on different sides of the base body plane G. The drive 4 is arranged on a first side G₁ of the base body 2, while the cutting disc 5 is arranged on a second side G₂ of the base body 2. The first side G₁ lies opposite the second side G₂.

The drive 4 has a housing 9 via which the drive 4 is fixed to the base body 2 in a fixing region 16 by fixing means 17. The fixing means 17 are in particular visible in FIG. 5. In comparison with a maximum width B of the base body 2, the fixing region 16 has a substantially smaller width b. For the width b, b≤0.1·B. Because the fixing region 16 has such a smaller width b, the drive 4 is arranged substantially closer to the base body 2, which counters a shift in the center of gravity of the abrasive cutter 1 in the direction of the first side G₁.

To control spark emission and protect an operator, a spark protection 7 is arranged on the base body 2 and partially surrounds the cutting disc 5.

FIG. 5 shows a section through the abrasive cutter 1 along cut line V-V in FIG. 2. In the exemplary embodiment shown, the cutting disc 5 is arranged on a cutting disc holder 3 via a first clamping element 13 a and a second clamping element 13 b. The clamping elements 13 a and 13 b each have a same diameter D. The cutting disc 5 is thus arranged between the two clamping elements 13 a and 13 b on the cutting disc holder 3 and attached thereto.

The spark protection 7 and the clamping element 13 a and 13 b define a cutting region 6 which is formed on a region of the cutting disc 5 that is not surrounded by the spark protection 7 or the first clamping element 13 a or second clamping element 13 b. The cutting region 6 is the region in which the cutting disc 5 comes or may come into contact with the rail (not shown) during the cutting process. The cutting region 6 forms a plane of symmetry S_(T).

The second clamping element 13 b has a passage opening via which this can be pushed onto the cutting disc holder 3 and thus come to rest against a stop 20 of the cutting disc holder 3.

To attach the first clamping element 13 a and hence attach the cutting disc 5 between the first and second clamping elements 13 a and 13 b, the cutting disc holder 3 has an axial bore 19 with internal thread in which a clamping element holder 18, in the form of a screw with an external thread, can be inserted. The first clamping element 13 a for this has a passage opening through which the threaded portion of the clamping element holder 18 can be passed. The first clamping element 13 a is fixed to an end 21 of the cutting disc holder 3 by the clamping element holder 18 after this has been screwed in.

The clamping elements 13 a and 13 b are configured such that they attach the cutting disc 5 by clamping, whereby on rotation of the cutting disc holder 3, the cutting disc 5 rotates via the two clamping elements. In the exemplary embodiment shown, the clamping elements 13 a and 13 b are each configured, starting from the rotary axis A₂ in the direction of their outer edges 22 a and 22 b, such that they are deformed towards the cutting disc 5 and sprung. Because of this deformation, a plurality of different cutting discs with different widths can be attached by means of the clamping elements 13 a and 13 b, since these deform depending on the width of the cutting disc 5 to be mounted, but still have a corresponding clamping effect.

An electric drive motor 15 with a drive shaft 10 is arranged in the housing 9 of the drive 4. In the exemplary embodiment shown, the electric drive motor 15 is configured as a brushless electric motor. The electric drive motor 15 has a rotor which comprises the drive shaft 10 and permanent magnets arranged thereon. The electric drive motor 15 furthermore comprises a stator having several electromagnets. The permanent magnets and the electromagnets are not illustrated in detail in the figures. The electric drive motor 15 has a power density P_(Spez)≤0.5 kW/kg. The drive shaft 10 defines the drive axis A₁. The drive 4 is attached to the fixing region 16 of the base body 2 via the fixing means 17 in the form of bolts.

In the exemplary embodiment shown, the drive 4 has a maximum transverse extent E which is equal to the diameter D of the clamping elements 13 a and 13 b. The maximum extent E is defined perpendicularly to the drive axis A₁ in the plane of symmetry S_(T). Because the maximum transverse extent E of the drive 4 is at most equal to the diameter D of the clamping elements 13 a and 13 b, it is ensured that the drive 4 does not protrude into the cutting region 6 and hence reduce this. The abrasive cutter 1 serves for use of cutting discs 5 with a maximum nominal diameter D_(N). The maximum nominal diameter D_(N) is in particular established by the spark protection 7. In particular, E≤0.5·D_(N).

In the exemplary embodiment shown, the drive shaft 10 is mounted on the housing 9 of the drive 4 via a first bearing 11, while the cutting disc holder 3 is mounted in the fixing region 16 of the base body 2 via a second bearing 12. The abrasive cutter 1 comprises a control unit 26 for actuating the drive 4.

In the exemplary embodiment shown, the drive shaft 10 of the drive 4 is configured as a hollow shaft in the engagement region 23, and has a receiving opening for receiving the cutting disc holder 3. The drive shaft 10 is connected by form fit to the cutting disc holder 3 by means of a feather key 14, whereby the drive 4 is directly coupled to the cutting disc holder 3 via the drive shaft 10. On rotation of the drive shaft 10, therefore, the cutting disc holder 3 also rotates. The cutting disc holder 3 defines the rotational axis A₂.

The function of the abrasive cutter 1 is as follows:

Firstly, the cutting disc 5 is mounted on the cutting disc holder 3 by the clamping elements 13 a and 13 b. For this, the second clamping element 13 b is pushed onto the cutting disc holder 3 and bears on the stop 20. Then the cutting disc 5 is pushed onto the cutting disc holder 3. Then the first clamping element 13 a is fixed to the cutting disc holder 3 by means of the clamping element holder 18, whereby the cutting disc 5 is clamped between the two clamping elements 13 a and 13 b. In this way, the cutting disc 5 is actively connected to the cutting disc holder 3. The drive shaft 10 is set in rotation by the control unit 26 which serves to control the drive 4. Because the drive shaft 10 is coupled directly to the cutting disc holder 3 by the feather key 14, the rotary motion of the drive shaft 10 is directly transmitted to the cutting disc holder 3. Since the cutting disc 5 is actively connected to the cutting disc holder 3 via the clamping elements 13 a and 13 b, the rotary motion of the cutting disc holder 3 is transmitted to the cutting disc 5. During the cutting process, the cutting disc 5 is successively worn away, reducing the diameter of the cutting disc 5. Because the maximum transverse extent E of the drive 4 is at most equal to the diameter D of the clamping elements 13 a and 13 b, the useful cutting region 6 extends up to the clamping elements 13 a and 13 b.

The electric drive motor 15 can be driven in rotation in different rotational directions by means of the control unit 26. The rotational direction may be set manually and/or automatically. The rotational direction is set for example by means of at least one control switch, preferably by means of a respective control switch, and/or automatically as a function of a holding position of the abrasive cutter 1, for example by means of a sensor.

With reference to FIG. 6, a second exemplary embodiment of the abrasive cutter 1 is described. In the second exemplary embodiment, the cutting disc holder 3 is formed in one piece with the drive shaft 10. The cutting disc holder 3 and the drive shaft 10 thus form a common shaft 24. Accordingly, the torque of the drive 4 is transmitted via the common shaft 24 to the first and second clamping elements 13 a and 13 b and hence to the cutting disc 5. The first bearing 11 and the second bearing 12 are supported on the housing 9. With respect to the further construction and further function, reference is made to the preceding exemplary embodiment.

A third exemplary embodiment of the invention is described below with reference to FIGS. 7 to 9. The base body 2 is formed extremely compactly. First handles 8 are fixedly arranged on the base body 2. In addition, second handles 8′ are arranged on the base body 2. The second handles 8′ are formed cylindrically and extend spaced apart from and parallel to each other. The second handles 8′ run substantially perpendicularly to the drive axis A₁ on a side of the base body 2 which faces away from the drive 4 relative to the first handles 8. The handles 8′ are connected together and stabilized by means of a spacer 27.

The electric drive motor 15 is arranged in the housing 9. The housing 9 is configured in two parts. The housing 9 comprises a pot-like first housing component 28 and a lid-like second housing component 29. The first bearing 11 is mounted in the first housing component 28, while the second bearing 12 is mounted in the second housing component 29. The second housing component 29 is attached in the fixing region 16 and releasably connected to the first housing component 28. The drive shaft 10 is connected integrally to the cutting disc holder 3. The drive axis A₁ and the rotational axis A₂ are arranged coaxially to one another.

The drive motor 15 is configured as a brushless electric motor. The drive motor 15 comprises a stator which is arranged rotationally fixedly relative to the housing 9. The stator 30 comprises electromagnets (not shown in detail) in the usual fashion. The stator 30 surrounds and delimits an interior in which a rotor 31 is arranged. The rotor 31 comprises permanent magnets 31′ and the drive shaft 10 in the usual fashion. The permanent magnets 31′ are attached, for example bonded, to the drive shaft 10. The rotor 31 may be driven in rotation about the drive axis A₁ by means of the stator 30.

The abrasive cutter 1 comprises a first temperature sensor 32 which is arranged inside the housing 9 on the electric drive motor 15. The first temperature sensor 32 is in signal connection with the control unit 26, and transmits thereto measurement values of a first temperature T₁ of the electric drive motor 15. The abrasive cutter 1 furthermore comprises a second temperature sensor 33. The second temperature sensor 33 is arranged on the control unit 26 and integrated together therewith in the base body 2. The second temperature sensor 33 is in signal connection with the control unit 26, and transmits thereto measurement values of a second temperature T₂ of the control unit 26.

In the control unit 26, a first temperature limit value T_(G1), for example 100° C., and a second temperature limit value T_(G2), for example 120° C., are predefined. The control unit 26 repeatedly compares the measurement values of the first temperature T₁ and the second temperature T₂ with the temperature limit values T_(G1) and T_(G2). If one of the temperatures T₁ and/or T₂ exceeds the first temperature limit value T_(G1), the consumable or emittable power P_(R) of the abrasive cutter 1 is reduced. The abrasive cutter 1 has a nominal power of 2 kW≤P≤3 kW, for example P=2.5 kW. If one of the temperatures T₁ and/or T₂ exceeds the first temperature limit value T_(G1), the emittable power P_(R) is reduced by means of the control unit 26, for example to P_(R)=0.7·P. The power is reduced for a predefined duration. If one of the temperatures T₁ and/or T₂ exceeds the second temperature limit value T_(G2), the abrasive cutter 1 is shut down by means of the control unit 26. The shut-down takes place for predefined duration. In this way, a temperature monitoring is implemented and an overheating of the drive 4 and/or control unit 26 is avoided.

The abrasive cutter 1 comprises an active cooling system 34 for cooling the drive 4 and/or the control unit 26. The active cooling system 34 produced a movement of a cooling medium L. The cooling medium L in the present exemplary embodiment is air. The cooling system 34 comprises an inflow channel 35, a fan wheel 36 and an outflow channel 37. The fan wheel 36 is attached to the common shaft 24 between the electric drive motor 15 and the second clamping element 13 b, and can be driven in rotation by means of the electric drive motor 15. The fan wheel 36 is for example formed in one piece with the second clamping element 13 b. The inflow channel 35 is formed L-shaped in cross-section. The inflow channel 35 firstly runs between the base body 2 and the housing 9 in the direction of the drive axis A₁. In the fixing region 16, the inflow channel 35 changes direction and in the fixing region 16 runs between the housing 9 and the second clamping element 13 b. The inflow channel 35 runs up to the fan wheel 36. The aspirated air L changes its flow direction at the fan wheel 36 and passes over the fan wheel 36 in the direction of the drive axis A₁. Then the outflow channel 37 begins. The outflow channel 37 runs from the fan wheel 36 between the base body 2 and the spark protection 7. The outflowing air L flows substantially perpendicularly to the drive axis A₁.

The electric drive motor 15 can be driven in rotation by means of the control unit 26 in a first rotational direction d₁ or in a second opposite rotational direction d₂. To set the respective rotational direction d₁, d₂, the abrasive cutter 1 has a first control switch S₁ and a second control switch S₂. If the first control switch S₁ is actuated, the electric drive motor 15 is driven in rotation in the first rotational direction d₁. If however the second control switch S₂ is actuated, the electric drive motor 15 is driven in rotation in the second rotational direction d₂.

When cutting through a rail, the abrasive cutter 1 is operated with a power P_(B) which is higher than the nominal power P. It takes between around 1 minute and 2 minutes to cut through a rail, so during this period the abrasive cutter 1 does not overheat. During rotation of the shaft 24, in particular during through-cutting of a rail, the electric drive motor 15 and the control unit 26 are cooled by means of the cooling system 34. If the abrasive cutter 1 is adequately cooled before cutting through a further rail, the further rail may be cut using the abrasive cutter 1 in the manner described without the abrasive cutter 1 overheating.

If the abrasive cutter 1 is greatly heated because of repeated cutting processes, then a safe operation of the abrasive cutter 1 is guaranteed by the temperature monitoring. If one of the temperatures T₁ and/or T₂ exceeds the first temperature limit value T_(G1), initially the power P_(B) is reduced to the power P_(R) and the abrasive cutter 1 is operated with the reduced power P_(R). This avoids further heating of the abrasive cutter 1 and subsequent overheating. If however one of the temperatures T₁ and/or T₂ exceeds the second temperature limit value T_(G2), the abrasive cutter 1 is shut down temporarily. With respect to the further structure and further function, reference is made to the preceding exemplary embodiments.

In general:

The abrasive cutter 1 may be connected to an external energy supply unit by means of an energy supply connection, and/or may comprise its own energy supply unit. An energy supply unit may for example be an accumulator or an accumulator arrangement. The energy supply unit may for example be attached to the base body 2 and/or be integrated in the base body 2. Preferably, the energy supply unit 2 can be recharged and/or exchanged. 

1. An abrasive cutter for cutting through a rail of a track, the abrasive cutter comprising: a base body; a cutting disc holder for mounting a cutting disc; and a drive for driving the cutting disc holder in rotation about a rotational axis, wherein: said drive is directly coupled to the cutting disc holder; said drive includes an electric drive motor; said electric drive motor (15 has a drive axis aligned with the rotational axis; said drive has a maximum transverse extent that is at most equal to a diameter of at least one clamping element for fixing the cutting disc to said cutting disc holder; and said electric drive motor has a power density P_(Spez), with P_(Spez)≤0.5 kW/kg.
 2. The abrasive cutter according to claim 1, wherein said electric drive motor has a drive shaft formed in one piece with said cutting disc holder.
 3. The abrasive cutter according to claim 1, wherein said electric drive motor has a drive shaft and wherein said drive shaft and said cutting disc holder are formed in two pieces.
 4. The abrasive cutter according to claim 1, wherein said drive is arranged on said base body.
 5. The abrasive cutter according to claim 1, wherein said drive has a housing, and wherein a first bearing is supported on said housing of said drive and a second bearing is supported on said base body.
 6. The abrasive cutter according to claim 1, wherein said drive has a housing, and wherein a first bearing and a second bearing are supported on said housing of said drive.
 7. The abrasive cutter according to claim 1, wherein said electric drive motor is a brushless electric motor.
 8. The abrasive cutter according to claim 1, wherein for the power density P_(Spez) applies: P_(Spez)≥0.8 kW/kg.
 9. The abrasive cutter according to claim 1, wherein for the power density P_(Spez) applies: P_(Spez)≥1.0 kW/kg.
 10. The abrasive cutter according to claim 1, further comprising at least one temperature sensor for determining a temperature of said drive and a temperature of a control unit.
 11. The abrasive cutter according to claim 1, further comprising a control unit for controlling said drive in dependence on a determined temperature.
 12. The abrasive cutter according to claim 1, further comprising a control unit configured to perform at least one of the following method steps: reducing an emittable power of said electric drive motor when a determined temperature exceeds a first temperature limit value; or shutting down said electric drive motor when a determined temperature exceeds a second temperature limit value.
 13. The abrasive cutter according to claim 1, further comprising a cooling system for cooling at least one of said electric drive motor or a control unit.
 14. A method for cutting through a rail of a track, the method comprising: providing an abrasive cutter according to claim 1; and cutting through the rail with a cutting disc that is driven in rotation by the abrasive cutter. 